1. Technical Field
The present invention relates generally to the field of communications, and in particular to a system and method for sending secure messages.
2. Description of the Related Art
Messages sent over communications networks are typically encoded in order to provide one or more cryptographic services such as authentication, encryption and non-repudiation. A message sender may digitally sign a message prior to transmission to a message recipient in order to authenticate the sender to the recipient, and to prove to the recipient that the message was not tampered with during transmission. The sender may also encrypt the message in order to prevent unauthorized viewing of the message by a party other than the recipient. In known systems, certificates are issued to users in order to support such cryptographic services. The certificates comprise information that may be used in algorithms that provide cryptographic services. For instance, the certificate may comprise information such as a public key for a user and a validity period for the certificate.
When the sender sends the message to one or more recipients, a messaging application, such as Microsoft Outlook™ or Lotus Notes™, retrieves the certificates for the recipients, and encodes the message to each recipient using information extracted from the certificates. As an example, the messaging application may use public key information extracted from the certificate in order to encrypt the message to the recipient.
Certificates may be stored in a Key Store that applications access in order to retrieve the certificates. If the certificate is not available in the Key Store, the sender may not be able to send the message until the certificate is made available. In order to do this, the sender has to retrieve the required certificates prior to sending the message. If the message has already been composed, the sender has to invoke a secondary application in order to retrieve the certificates, and then return to the messaging application in order to send the message.
The certificates may also become invalid over time. For instance, they may be revoked if certain information, such as the private key associated with the certificate, becomes compromised. They may also simply expire. If the message is encoded with an invalid certificate, recipients may not be able to authenticate the sender or be able to decrypt the message if it was signed or encrypted with a private key that is associated with an invalid public key.